Seachem Iron Multitest stays clear? - The Planted Tank Forum
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post #1 of 15 (permalink) Old 02-18-2019, 01:54 AM Thread Starter
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Seachem Iron Multitest stays clear?

I tried using the seacmhem iron multitest, and tried both the normal and low range: https://www.amazon.com/Seachem-Multi.../dp/B0006JLZ0O

However, even after waiting three hours, all that happened was that I saw small black specs in clear white liquid in both. It was supposed to turn yellow for nothing, and pinker the more iron there was.

Did I do something wrong, or is the test messed up? I double checked the instructions and performed it correctly. I dose with CSM+B three times a week @ 200mg for a 22 gallon long. There should definitely be iron present right?

Btw the reason I'm testing it because I'm getting staghorn algae while on the EI method and I've read that too much iron is the cause: https://www.aquasabi.com/aquascaping...staghorn-algae
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post #2 of 15 (permalink) Old 02-18-2019, 04:37 AM
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I've had the same experience. Edward reports that the Seachem test is highly insensitive to EDTA or DTPA, requiring up to 24 hours to register properly with EDTA or 48 for DTPA (and showing about half the response even then.)

I've done some serious scrounging around online and it's surprisingly difficult to find information on how he Seachem test actually works. This makes it tough to know if there is anything you can do to speed up the test, such as adding something to break up the chelate or heating the test water, that won't interfere with the test. I'm going to continue scrounging.

So, I've dug a little more. Here is my best wild guess, which I'll emphasize up front could be completely wrong.

The reagent that keeps coming up in my internet searches is bathophenanthroline, which reacts with ferrous iron to produce an intense magenta color. That sounds like the Seachem test, all right. The stuff is pretty insoluble in neutral or alkaline water, but slightly soluble in acid water. I tested the pH of a little of the Seachem reagent in water, and, sure enough, it's quite acidic. My wild guess (emphasize again: my back-engineering of the Seachem test could easily be wrong) is that Seachem is a mixture of an acidifying agent, probably sodium acid sulphate (because it's cheap, nontoxic, and won't interfere with the test) with a small amount of bathophenanthroline. The other common and cheap nontoxic acidifying agent, citric acid, would interfere with the test.

Bathophenanthroline is a fairly expensive compound to manufacture, because it's a fairly complex organic compound. For those who are entertained by such things:


One site gives a spot price for the stuff of $178 for ten grams, but that may be pharmaceutical grade (it's used in medicine to test for iron in urine and blood serum), which will likely be more expensive than the technical grade good enough for a mass-produced aquarium test kit. Plus you only need a little in each container of test reagent -- the white powder you measure into the cuevettes is probably mostly the acidifying agent. The bathophenanthroline would still account for much of the cost of an iron test kit. The stuff is not notably toxic, so it's something Seachem can sell to aquarists without fear of liability.

Bathophenanthroline is a chelating agent, like citric acid, gluconate, EDTA, and DTPA, but with the property of turning intense magenta when it grabs onto a ferrous iron ion. So it's going to be competing with any chelating agent already in your aquarium water. I scrutinized the instructions that come with the Seachem kit; they claim their test works with "most" chelated iron but you have to be patient. That's the kind of careful wording you always have to watch out for. I suspect it does okay with citrated or gluconated iron, since those are relatively weak chelating agents, but it has a tough time competing with EDTA or DTPA for the ferrous iron.

Probably goes without saying, but it's almost certainly not worth the effort to try to order your own bathophenanthroline and acidifier to make your own iron test kit. Yours will work no better, you'll have to calibrate it, and you won't be able to negotiate anything better than the spot price for the reagents.

Any way to speed up the test? Probably not. Anything that can pry the iron away from the EDTA will likely also pry it away from the bathophenanthroline. EDTA is a pretty tough compound; living organisms can break it up to release the iron (else EDTA iron would be useless as fertilizer) but it's mostly destroyed in the environment by ultraviolet light from the sun. Which would also destroy bathophenanthroline.

Maryland Guppy reports that Hanna has a test that seems to do okay detecting EDTA-chelated iron. If this is the test in question, then it uses phenanthroline, a simpler compound related to bathophenanthroline that turns orange rather than red. The test is (surprise!) a bit pricier, but if I continue to see a need to test iron, I may buy a kit and see how it works for me.

Last edited by Darkblade48; 02-19-2019 at 11:00 PM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #3 of 15 (permalink) Old 02-18-2019, 03:50 PM
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If your interested in an iron test you might want to look at the hanna iron Checker:

https://hannainst.com/hi746-iron-low...eckerr-hc.html

It cost a little over twice as much as the Seachem test ($20 for Seachem, $50 for Hanna but gives you a digital reading in ppm in only a few minutes. Note you do need deionized water for the test. They also make a great phosphate, alkalinity and ammonia checker.
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post #4 of 15 (permalink) Old 02-18-2019, 04:37 PM Thread Starter
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Amazing info kgbudge, and thank you for the link Surf! I'll give the other test a try and let the seachem test sit all day/night.

The thing that confuses me the most about the seachem test is that it was supposed to turn yellow with no findings, but it stayed clear. Wondering if it will turn yellow over night.
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post #5 of 15 (permalink) Old 02-18-2019, 05:10 PM
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Quote:
Originally Posted by Ddrizzle View Post
The thing that confuses me the most about the seachem test is that it was supposed to turn yellow with no findings, but it stayed clear. Wondering if it will turn yellow over night.
I've never seen it turn yellow, whether it eventually detected iron nor not.

I can't say I've extensively shopped, but from what I came across in my Internet dive, it seems like the Hanna test is probably the gold standard of what an ordinary aquarist can reasonably budget. The complete test is not only the reagents, but a colorimeter to read the intensity of the magenta color and give you a precise numerical measurement. (Note that I did not say "accurate"; hardcore techies will understand the difference; but I've no reason to doubt that it's reasonably accurate as well.)
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post #6 of 15 (permalink) Old 02-18-2019, 09:14 PM
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Ö give you a precise numerical measurement. (Note that I did not say "accurate"; hardcore techies will understand the difference; Ö
Gazillion digits instead of the factual value?

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post #7 of 15 (permalink) Old 02-18-2019, 10:10 PM
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Originally Posted by kgbudge View Post
If this is the test in question, then it uses phenanthroline, a simpler compound related to bathophenanthroline that turns orange rather than red. The test is (surprise!) a bit pricier, but if I continue to see a need to test iron, I may buy a kit and see how it works for me.
This is the checker https://hannainst.com/hi721-iron.html

Phenanthroline, sodium metabisulfite, and sodium dithionite.

Get the test that reads up to 5ppm, you never know what people will dose.
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Last edited by Maryland Guppy; 02-18-2019 at 10:12 PM. Reason: edit
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post #8 of 15 (permalink) Old 02-18-2019, 10:34 PM
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Gazillion digits instead of the factual value?
Just so.

In this case, it looks like it reads to tenths of a milligram per liter. That may not be unreasonable.

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Originally Posted by Maryland Guppy View Post
This is the checker https://hannainst.com/hi721-iron.html

Phenanthroline, sodium metabisulfite, and sodium dithionite.

Get the test that reads up to 5ppm, you never know what people will dose.
Yep, that sounds right. Phenanthroline as the indicator, and sodium dithionite to keep the iron in the reduced state. Sodium metabisulfite is a reducing agent and a mild acidifier; I would have guessed sodium metabisulfate instead, but I guess the reducing power more important than acidification. I got wondering if either of these helps break down EDTA, but I found a paper online that says they are often used with EDTA to remove rust stains from old documents. It would be interesting to know why folks see better results for this than for the Seachem test.
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post #9 of 15 (permalink) Old 02-18-2019, 11:25 PM
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In this case, it looks like it reads to tenths of a milligram per liter. That may not be unreasonable.
Actually hundredths, from testing the same vials (one without reagent and one with) up to 10 times the unit seems to be within 0.04 consistently.
Guess I should take a sample to work and test it against a high end Hach Colorimeter?

The learning curve is getting all of the reagent out of the packet.
Tap to get it in the center, a bend in the middle and don't crease it.

Plenty of accuracy for testing our tanks.
Purchased this unit because it was the one thing that so much controversy was applied to and I wanted a fairly accurate way to measure.
Mostly likely the only "Checker" of this style I will buy.
The cheap test kits for everything else is close enough.
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post #10 of 15 (permalink) Old 02-19-2019, 04:20 AM
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Note hanna sells 2 versions of the meter. High range and a low range. I purchased the low range. The accuracy of this meter is listed on the link I provided. It is +/-20 PPB +/-%% of reading. resolution is 1ppb with a range of 0 to 999 PPB.

As to getting the reagent out of the packet is a little tricky but after trying various ways I found the Hanna recommended way is probably the best. Tap the edge oof the packet on hard flat surface with one of the two cut ends horizontal at the top. Then rotate the packet so the other cut end is horizontal at the top and tap again. The cut on the cut end and open the packet. Still it does take some practice.

Last edited by Surf; 02-19-2019 at 04:44 AM. Reason: text correction
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post #11 of 15 (permalink) Old 02-24-2019, 09:11 PM Thread Starter
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Reporting back that the hanna test does indeed work, very well. I got the high iron version not knowing there were two versions. Didn't matter since it still reads from 0 to 5ppm.

So, my iron is high. It's at least 1.05, but probably greater due to me losing some reagent when trying to pour it in. People weren't joking when they said the reagent packets suck. Can't complain about the rest of the product though.

My iron is probably high due to dosing seachem micros AND CSM+B at the same time. I was a noobie at the time and didn't understand ferts.
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post #12 of 15 (permalink) Old 02-24-2019, 09:16 PM
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Glad to hear this. I found that I got practically no detection of iron with the Seachem test against a test solution of DTPA-chelated iron, even after letting it sit for three days.
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post #13 of 15 (permalink) Old 02-24-2019, 11:15 PM
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FWIW I changed my substrate yesterday and dosed macros since water was zero. (RODI)

Dosed my micro dose today to .25ppm of Fe DTPA in the water column and tested 10 minutes later and Hanna checker reads .24ppm.

For viewing the "invivsble" this ain't too bad!
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Last edited by Maryland Guppy; 02-24-2019 at 11:18 PM. Reason: edit
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post #14 of 15 (permalink) Old 03-26-2019, 10:00 PM
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I've discovered that trying to use the low-range test was counterproductive. It never shows anything. The high-range takes overnight to develop, but then gives a useful reading.

I'm guessing this is because the low-range test actually dilutes the reagents more than the high-range, in its effort to let you look through a deeper water column.
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post #15 of 15 (permalink) Old 03-28-2019, 01:31 AM
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I found the SeaChem iron test totally useless. I have never detected any color change, even after dosing iron in my tank water. It has been sitting in my shelf unused for over a year. I rely on dosing calculation and my water company reports than testing to guess my iron concentration.
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